Tohatsu began producing a single-cylinder 50cc racing bike in 1962, called the Rumpet CR. See picture below, courtesy of Classic Racer (it's the one on the right) :

These were raced in the UK and in Switzerland. In the UK, the Simmonds brothers were the drivers. These machines were hopelessly uncompetitive and seized continuously. I remember seing one with its Swiss owner repairing the machine during a hillclimb at Freiburg. It was his third piston of the day.Shortly after this, Tohatsu designed and built a 50cc twin-cylinder with a 5-speed gear change and dry clutch. Probably no more than 6 were ever built. The Simmonds got at least one, while another was in Switzerland. The others raced in Japan and Malaysia. Again they were slow and unreliable, but oh so pretty... a pair survives today and runs fine using modern alloys.

These were not fast enough to compete with the Suzuki, Honda or even the Derbi production racers of the time. Indeed they lacked the magic ingredient: a disc valve induction allowing much longer intake timing, as well as the magic "third" transfer port facing the exhaust. At the time, the Japanese were learning, fast. Tohatsu was not learning fast enough.

In 1964, Tohatsu also produced a very limited number of piston-port 125cc twins, the subject of the question above. These were beautiful machines with well designed chassis, large Honda-style brakes and 6-speed transmissions, but they could not really compete with even a good Bultaco TSS, let alone a Honda CR93. However Dave Simmonds was a heck of a good driver and won a few short-circuit races with his between it being broken. Eventually he ran out of spares and the Tohatsus were parked in favor of other Japanese machinery.

In France, Jacques Roca, the Derbi importer, got hold of one of those 125cc Tohatsus and replaced the seizing-prone cylinders by two from a Derbi 50c and a Derbi 75cc. The mix did not work too well either but was really fast while it lasted. Tohatsu was at the time struggling for its existence and the racing programme had cost them dearly without the hoped for success. In 1965, Bridgestone absorbed Tohatsu and put its engineers to work on their own road and racing machines. The Bridgestone 175 and 350 roadsters were brilliant designs with disc valves, fast, reliable and handling well. But the other large Japanese motorcycle manufacturers did not see too well of their tire supplier competing with them, so in 1967 after Honda forced their hand, they closed their motorcycle production. A great loss in my opinion.Regards,

as a point of interest,in the late 60's an american actor named richard wyler(the man from interpol)also did a bit of road racing in england using tohatsus,i know this as i bought his thames 15cwt van off of cyril jones in i think 1967/8,it had wylers name in the log book.

A final note: the Tohatsu engineer who designed the 50cc twin also designed the Bridgestone 50cc Twin with disc valve and 10-speed gearbox for the giant tire manufacturer. Four of these beautiful machines were built but only raced at the 1966 Japanese Grand Prix where they were no match for the Suzuki and Honda twins. Here is one of the two survivors:

At the same time, Kawasaki was also planning a 50cc twin as well as building a yet uncompetitive 125cc twin. History shows that Dave Simmonds after two awful years with the Kawasaki breaking its crankshaft and seizing pistons at about every race, somehow managed to win the world championship with it a year later after the works pulled out, using the very last spares on the planet to do so.Poor Dave was then killed in a fire inside his trailer. Honda AND Suzuki planned new 50cc 3-cylinder machines for the 1968 season, but as all other Japanese manufacturers, pulled out of racing altogether as the Japanese economy began a recession and capital was needed to develop new projects for public consumption, leaving several machines in the hands of private racers such as Dave Simmonds, Hans Anscheidt and few others.Honda had already built a 125cc 5-cylinder machine made from the cylinders of their 50cc twin plus three, and this 25000RPM machine had won the 1966 title in the hands of Luigi Taveri. The next machine was goind to be a 125cc V8 but only saw life as a sketch on a piece of paper. What could have been...

Originally posted by T54 A final note: the Tohatsu engineer who designed the 50cc twin also designed the Bridgestone 50cc Twin with disc valve and 10-speed gearbox for the giant tire manufacturer. Four of these beautiful machines were built but only raced at the 1966 Japanese Grand Prix where they were no match for the Suzuki and Honda twins. Here is one of the two survivors:

At the same time, Kawasaki was also planning a 50cc twin as well as building a yet uncompetitive 125cc twin. History shows that Dave Simmonds after two awful years with the Kawasaki breaking its crankshaft and seizing pistons at about every race, somehow managed to win the world championship with it a year later after the works pulled out, using the very last spares on the planet to do so.Poor Dave was then killed in a fire inside his trailer. Honda AND Suzuki planned new 50cc 3-cylinder machines for the 1968 season, but as all other Japanese manufacturers, pulled out of racing altogether as the Japanese economy began a recession and capital was needed to develop new projects for public consumption, leaving several machines in the hands of private racers such as Dave Simmonds, Hans Anscheidt and few others.Honda had already built a 125cc 5-cylinder machine made from the cylinders of their 50cc twin plus three, and this 25000RPM machine had won the 1966 title in the hands of Luigi Taveri. The next machine was goind to be a 125cc V8 but only saw life as a sketch on a piece of paper. What could have been...

Sorry to have to correct you but Dave was killed fighting a fire in someone elses caravan at a circuit just outside Paris, Rungis I believe, in 1972.I won my first national race against Dave, who was riding his 125 Tohatsu, at Castle Combe after race long dice. He was a wonderful rider to race with and a real human being. Some years later I built a 125 utilising a Tohatsu chassis and Yamaha motor. Handled beautifully and very fast but couldn't keep a crank in it!

Sorry to have to correct you but Dave was killed fighting a fire in someone elses caravan at a circuit just outside Paris, Rungis I believe, in 1972.I won my first national race against Dave, who was riding his 125 Tohatsu, at Castle Combe after race long dice. He was a wonderful rider to race with and a real human being. Some years later I built a 125 utilising a Tohatsu chassis and Yamaha motor. Handled beautifully and very fast but couldn't keep a crank in it!

I haven't involved myself in this thread because I can't add anything of any use but I am so glad that somebody put the Tohatsu's on here. I always thought they were beautiful little things. Dave and Mike Simmonds made their names on them despite their awful habit for seizing. A two stroke rider's reflexes had to be so quick those days as you knew that every time you closed the throttle, their was a pretty fair chance that the thing would lock up.

T54, fascinating stuff on the technical front. The 350 Bridgestone was always a rocket and I am sure I can remember a Welsh guy going very, very quickly on one in the UK in about '67 or '68. Can't give you a name though.

Rod, yes you're right about the caravan. It was Jack Findlays caravan. I believe his wife Juli (Bill Boddice's daughter)was also badly burned.

Sorry for the error. I wrote from fading memory and did not research it.

The problem with Yamaha 125 cranks was very well known in the USA too. I believe that I am one of the very few who actually resolved it, and I have a long string of wins between 1974 and 1976 to show for it before I was the recipient of a works Morbidelli on loan from the Pesaro concern.

The AS1/AS3/TA125 cranks were often assembled "pinched" or too loose when the crankcases were bolted together, despite precise thickness measurements of the crank assembly and the cases. If pinched, the crank tail on the ignition side would wobble, causing the left-side rod bearing to heat up and seize. If loose, the crank would move sideways and eventually allow one flywheel to move on its pin, causing again excessive heat in one or both of the rod bearings. Also the main bearings would turn in their location and pinche the crank. Another problem was the stacking of the drive pinion side, often pulling the right-side flywheel. Assembly must always being on the pinion side, with the pinion stacked and bolted solid. The the center labyrith can be set. When the outer case is slowly bolted in, the magneto tail must be pulled at the dame time. I made special tools for this and still retain them to this day.
To solve these problems, I drilled and tapped holes in the cases and locked the main bearings in place with flush hex screws, then did the same on the crank pins so that they could not turn. Last, I used FAG bearings for the rods, much better than the Yamaha "gold" parts. My cranks as well as of the few other engines I modified for several racers lasted up to 20 races before replacement. Next I criss-crossed the chrome barrels (yes it can be done) for better oil retention. No more seizures.

We also had the fastest TA/AS3 engines of any, including that of young Randy Mamola...
Our bike won many of the AFM races in 1974 to 1976 as well as the CMC title in 1975.
If anyone is racing a TA today in vintage events, I have a few mods for the clutch and crank I can share by PM. I also have a box full of brand new spares for these engines as well as a few cycle parts.

Back to the Tohatsu, the 125cc chassis was indeed a beauty and frankly SO much better than what Yamaha had to offer in their twist-O-flex TA.

Originally posted by T54 Sorry for the error. I wrote from fading memory and did not research it.

The problem with Yamaha 125 cranks was very well known in the USA too. I believe that I am one of the very few who actually resolved it, and I have a long string of wins between 1974 and 1976 to show for it before I was the recipient of a works Morbidelli on loan from the Pesaro concern.

The AS1/AS3/TA125 cranks were often assembled "pinched" or too loose when the crankcases were bolted together, despite precise thickness measurements of the crank assembly and the cases. If pinched, the crank tail on the ignition side would wobble, causing the left-side rod bearing to heat up and seize. If loose, the crank would move sideways and eventually allow one flywheel to move on its pin, causing again excessive heat in one or both of the rod bearings. Also the main bearings would turn in their location and pinche the crank. Another problem was the stacking of the drive pinion side, often pulling the right-side flywheel. Assembly must always being on the pinion side, with the pinion stacked and bolted solid. The the center labyrith can be set. When the outer case is slowly bolted in, the magneto tail must be pulled at the dame time. I made special tools for this and still retain them to this day.To solve these problems, I drilled and tapped holes in the cases and locked the main bearings in place with flush hex screws, then did the same on the crank pins so that they could not turn. Last, I used FAG bearings for the rods, much better than the Yamaha "gold" parts. My cranks as well as of the few other engines I modified for several racers lasted up to 20 races before replacement. Next I criss-crossed the chrome barrels (yes it can be done) for better oil retention. No more seizures.

We also had the fastest TA/AS3 engines of any, including that of young Randy Mamola... Our bike won many of the AFM races in 1974 to 1976 as well as the CMC title in 1975. If anyone is racing a TA today in vintage events, I have a few mods for the clutch and crank I can share by PM. I also have a box full of brand new spares for these engines as well as a few cycle parts.

Back to the Tohatsu, the 125cc chassis was indeed a beauty and frankly SO much better than what Yamaha had to offer in their twist-O-flex TA.

T54, I think youre going to have to start a thread on the 125 Yamaha at some point.

Just as an aside I can't remember us having the same trouble with the TD2. Yet that surely had a larger version of the same AS1 bottom end with vertically split crank cases and centre labyrinth etc. Does my memory fail me?

No, you are correct and the same problems afflicted the TD1, TD2, TR1 and TR2 as well as all vertically-split Yamaha racers. The Tohatsu had THREE set of cases, a very good design really where the center case retained the crank and the outer cases could be spaced properly. But at the time, few actually capitalized on this design advantage.
And yes, we should have a thread about 125cc Japanese machinery... if anyone cares
I can really help anyone racing those bikes if they have problems.

Sorry to have to correct you but Dave was killed fighting a fire in someone elses caravan at a circuit just outside Paris, Rungis I believe, in 1972.I won my first national race against Dave, who was riding his 125 Tohatsu, at Castle Combe after race long dice. He was a wonderful rider to race with and a real human being. Some years later I built a 125 utilising a Tohatsu chassis and Yamaha motor. Handled beautifully and very fast but couldn't keep a crank in it!

Further to the above, I've just found this pic taken at Castle Combe during the race.

Hi Warren
welcome to the forum
how about posting about yourself here:http://forums.autosport.com/index.php?showtopic=109425
if you read through, you will find some very well known riders on here as well as club riders, photographers, team owners, spectators, in fact folk form all aspects of the sport.

Ah Tohatsu, what a pretty 125cc. Nobody has mentioned Wallingford dealer Jim Pink, who raced a 125. I always wondered if he bought it because it was pink. I remember passing him on the straight at Snetterton, & being really disappointed to see how slow it was. The engine sounded OK. I almost sure I was on a Bantam, but could have been a 125 Bultaco or a CR110 50cc Honda.

I seem to remember that Dave Simmonds father worked for BOAC & brought his 50cc twin from Japan as hand luggage. Surely,he must have had some sort of factory support or access to parts & information, because he was the only one who could make them work.

I was interested to hear that they were absorbed into Bridgestone. Presumably, Tohatsu outboard motors are manufactured by Bridgestone.

Mick Walkers book Classic Japanese Racing Motorcycles has a bit of information on Tohatsu especially a 2 page pic of the 50cc twin engine and the 3 piece crankcases. Its funny we were only talking about Tohatsu outboard motors at work today.

Hi I am a new member , I am very interested in the history of Tohatsu Motorcycles After completing a long restoration on my own 1963 Tohatsu 106y 125cc racer .Has anyone information on the Richard Wyler /Cyril Jones photos /progammes Thanks Howard

A new member here; Thanks to Warren the Yamanatc for his posting of May 31st. last year. First time I've seen a CR50 and it made my day.

I have several Tohatsui. (if that would be the spelling for several.) Anyway in my collection is a CR50 in many pieces. I would be interested in any information and pictures anyone might have. Thanks; the Den - cd3tohatsu.

Hi I am a new member , I am very interested in the history of Tohatsu Motorcycles After completing a long restoration on my own 1963 Tohatsu 106y 125cc racer .Has anyone information on the Richard Wyler /Cyril Jones photos /progammes Thanks Howard

www.CycleWak.com site has an expired domain name now. I wanted to contact them about Tohatsu bikes/parts that I may be acquiring soon.

Hi I am a new member , I am very interested in the history of Tohatsu Motorcycles After completing a long restoration on my own 1963 Tohatsu 106y 125cc racer .Has anyone information on the Richard Wyler /Cyril Jones photos /progammes Thanks Howard

Hi, My name is Cal Stender
I'm in California, USA. and new to this forum. Great info. Thanks.
I have two 50cc 1963 Tohatsus. There are quite a few in the States including Racers.
I just started a Tohatsu Motorcycle Yahoo Group. Dedicated to keeping these great old machines alive! Anyone who owns a Tohatsu or is a Fan. Please join. We appreciate any knowledge you can share and always love those old pictures and stories.